Ferns grew already in the Carboniferous, about 400 million years ago. At that time, they grew still tree high. Therefore, they are usually referred as tree ferns. Together with club mosses and horsetail , they formed huge forests. In German the male fern called worm fern. It gets the name not only because of the worm-like shape of its sori but also because he was formerly used as a remedy for tapeworm infestation.